So in a nutshell here is how our subscription management page works. In our Email Footers we changed the unsubscribe link to include this query string at the end
the key part is the elq string with the recipientid value. This is what makes the correlation between the user and their contact record (since cookies don't always work).
The next piece to the puzzle is creating a javascript loop that checks to see if the associated recipientid can be linked to an email (this is a standard WDL)
If it finds the email it uses a second WDL to find their subscriptions and the process is basically complete and the form auto populates.
If it can't find an email then it will display a dialog asking the user to enter their email. Once the user enters their email it calls that second WDL to find their subscriptions and auto populates.
We haven't verified that this works in Safari but it is known to work in the latest versions of FF, IE, and Chrome and should work in any browser that has javascript enabled.